Upload
others
View
4
Download
0
Embed Size (px)
Citation preview
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Java and C IICSE 351 Spring 2017
Instructor:
Ruth Anderson
Teaching Assistants:
Dylan Johnson
Kevin Bi
Linxing Preston Jiang
Cody Ohlsen
Yufang Sun
Joshua Curtis
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Administrivia
Lab 5 – Due TONIGHT! Fri 6/2
Course evaluations now open
Please fill out evals for lecture AND separate eval for section!
Final Exam: Wed, June 7, 2017 2:30-4:20pm in our regular lecture room
2
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Hardware Hardware
Implementing Programming Languages
Many choices in how to implement programming models
We’ve talked about compilation, can also interpret
Interpreting languages has a long history Lisp, an early programming language, was interpreted
Interpreters are still in common use: Python, Javascript, Ruby, Matlab, PHP, Perl, …
3
Your source code
Binary executable
Interpreter implementation
Interpreter binary
Your source code
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
An Interpreter is a Program
Execute the source code directly (or something close)
Simpler/no compiler – less translation
More transparent to debug – less translation
Easier to run on different architectures – runs in a simulated environment that exists only inside the interpreter process Just port the interpreter
Slower and harder to optimize
4
Interpreter implementation
Interpreter binary
Your source code
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Interpreter vs. Compiler
An aspect of a language implementation A language can have multiple implementations
Some might be compilers and other interpreters
“Compiled languages” vs. “Interpreted languages” a misuse of terminology But very common to hear this
And has some validation in the real world (e.g. JavaScript vs. C)
Also, as about to see, modern language implementations are often a mix of the two Compiling to a bytecode language, then interpreting
Doing just-in-time compilation of parts to assembly for performance
5
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
“The JVM”
Java programs are usually run by a Java virtual machine (JVM)
JVMs interpret an intermediate language called Java bytecode
Many JVMs compile bytecode to native machine code • Just-in-time (JIT) compilation
• http://en.wikipedia.org/wiki/Just-in-time_compilation
Java is sometimes compiled ahead of time (AOT) like C
6
Note: The JVM is different than the CSE VM running on VMWare. Yet another use of the word “virtual”!
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Compiling and Running Java
The Java compiler converts Java into Java bytecodes Stored in a .class file
Save your Java code in a .java file
To run the Java compiler: javac Foo.java
To execute the program stored in the bytecodes, Java bytecodes can be interpreted by a program (an interpreter) For Java, the JVM is the interpreter
java Foo runs the Java virtual machine• Loads the contents of Foo.class and interprets the bytecodes
7
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Virtual Machine Model
8
High-Level Language Program(e.g. Java, C)
Virtual Machine Language(e.g. Java bytecodes)
Native Machine Language
(e.g. x86, ARM, MIPS)
Bytecode compiler(e.g. javac Foo.java)
Virtual machine (interpreter)(e.g. java Foo)
Ahead-of-timecompiler
JITcompiler
run time
compile time
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Java Bytecode
Like assembly code for JVM,but works on all JVMs Hardware-independent!
Typed (unlike x86 assembly)
Strong JVM protections
9
0 1 2 3 4 n
variable table
operand stack
constantpool
Holds pointer this
Other arguments to method
Other local variables
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
JVM Operand Stack
10
iload 1 // push 1st argument from table onto stack
iload 2 // push 2nd argument from table onto stack
iadd // pop top 2 elements from stack, add together, and
// push result back onto stack
istore 3 // pop result and put it into third slot in table
mov 8(%ebp), %eax
mov 12(%ebp), %edx
add %edx, %eax
mov %eax, -8(%ebp)
Compiledto x86:
Bytecode:
0 1 2 3 4 n
constantpool
variable tableoperand stack
JVM:
Holds pointer this
Other arguments to methodOther local variables
‘i’ = integer,‘a’ = reference,‘b’ for byte,‘c’ for char,‘d’ for double, ...
No registers or stack locations!All operations use operand stack
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
A Simple Java Method
11
Method java.lang.String getEmployeeName()
0 aload 0 // "this" object is stored at 0 in the var table
1 getfield #5 <Field java.lang.String name>
// getfield instruction has a 3-byte encoding
// Pop an element from top of stack, retrieve its
// specified instance field and push it onto stack
// "name" field is the fifth field of the object
4 areturn // Returns object at top of stack
2A B4 00 05 B0As stored in the .class file:
http://en.wikipedia.org/wiki/Java_bytecode_instruction_listings
0
aload_0 getfield 00 05 areturn
1 4Byte number:
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Class File Format
Every class in Java source code is compiled to its own class file
10 sections in the Java class file structure: Magic number: 0xCAFEBABE (legible hex from James Gosling – Java’s inventor)
Version of class file format: The minor and major versions of the class file
Constant pool: Set of constant values for the class
Access flags: For example whether the class is abstract, static, final, etc.
This class: The name of the current class
Super class: The name of the super class
Interfaces: Any interfaces in the class
Fields: Any fields in the class
Methods: Any methods in the class
Attributes: Any attributes of the class (for example, name of source file, etc.)
A .jar file collects together all of the class files needed for the program, plus any additional resources (e.g. images)
12
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
DisassembledJava Bytecode
13
Compiled from Employee.java
class Employee extends java.lang.Object {
public Employee(java.lang.String,int);
public java.lang.String getEmployeeName();
public int getEmployeeNumber();
}
Method Employee(java.lang.String,int)
0 aload_0
1 invokespecial #3 <Method java.lang.Object()>
4 aload_0
5 aload_1
6 putfield #5 <Field java.lang.String name>
9 aload_0
10 iload_2
11 putfield #4 <Field int idNumber>
14 aload_0
15 aload_1
16 iload_2
17 invokespecial #6 <Method void
storeData(java.lang.String, int)>
20 return
Method java.lang.String getEmployeeName()
0 aload_0
1 getfield #5 <Field java.lang.String name>
4 areturn
Method int getEmployeeNumber()
0 aload_0
1 getfield #4 <Field int idNumber>
4 ireturn
Method void storeData(java.lang.String, int)
…
> javac Employee.java
> javap -c Employee
http://en.wikipedia.org/wiki/Java_bytecode_instruction_listings
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Other languages for JVMs
JVMs run on so many computers that compilers have been built to translate many other languages to Java bytecode: AspectJ, an aspect-oriented extension of Java
ColdFusion, a scripting language compiled to Java
Clojure, a functional Lisp dialect
Groovy, a scripting language
JavaFX Script, a scripting language for web apps
JRuby, an implementation of Ruby
Jython, an implementation of Python
Rhino, an implementation of JavaScript
Scala, an object-oriented and functional programming language
And many others, even including C!
14
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
Microsoft’s C# and .NET Framework
C# has similar motivations as Java Virtual machine is called the
Common Language Runtime
Common Intermediate Language is the bytecode for C# and other languages in the .NET framework
15
CSE369, Autumn 2016L01: Intro, Combinational Logic CSE351, Spring 2017L27: Java and C II
We made it! ☺😎😂
16
car *c = malloc(sizeof(car));
c->miles = 100;
c->gals = 17;
float mpg = get_mpg(c);
free(c);
Car c = new Car();
c.setMiles(100);
c.setGals(17);
float mpg =
c.getMPG();
get_mpg:
pushq %rbp
movq %rsp, %rbp
...
popq %rbp
ret
Java:C:
Assembly language:
Machine code:
0111010000011000
100011010000010000000010
1000100111000010
110000011111101000011111
Computer system:
OS:
Memory & dataIntegers & floatsx86 assemblyProcedures & stacksExecutablesArrays & structsMemory & cachesProcessesVirtual memoryMemory allocationJava vs. C